1. Field of the Invention
This invention relates to a printer in which a printing head is moved to a predetermined initial position by driving a stepping motor at the time of initial processing.
2. Prior art
In many printers, a position for determining an initial printing position has been set at an end portion of a traveling area of a printing head. The printing head is moved to the initial printing position when power is supplied or a reset command is input before general printing operation is started.
In order to correctly move the printing head to the initial position, a stepping motor, which can correctly control the rotating angle, is used as a printing head driving motor. In the initial processing operation, however, the known speed-up and slow-down control cannot be executed because the traveling distance of the printing head is indeterminate. To cope with this, the stepping motor is driven by a known method referred to as self-starting. Namely, a rotor salient pole of the stepping motor stops temporarily at a stable point (which is provided between each excitation pole for one-phase exciting method and between two excitation poles for two-phase exciting method) while it is rotating in synchronism with control pulse signals. (This movement is hereinafter referred to as step driving.) Thus, the stepping motor is driven in the condition that starting, stopping and inversion of rotating direction can be instantaneously executed to move the printing head to the initial position.
In the above-mentioned printer, the stepping motor is driven by the relatively high-level constant current required to compensate for the torque necessary to move the printing head at a high speed for high-speed printing, etc. When the stepping motor is thus actuated by self-starting, noise is apt to be generated. Therefore, when the traveling distance of the printing head to the initial position is relatively long, an uncomfortable pulse sound may be generated.